⚖️ BMI & Body Fat Calculator
Enter your weight, height, age, and sex to see your Body Mass Index and category alongside an estimated body-fat percentage — a quick snapshot for tracking body composition.
⚖️ Calculate BMI & Body Fat
What is a BMI & Body Fat Calculator?
It gives you two common body-composition markers at once. Body Mass Index relates your weight to your height and places you in a standard category, while the Deurenberg equation estimates your body-fat percentage by adjusting that BMI for your age and sex — no calipers or scans required.
Athletes track body composition to guide nutrition, monitor training phases, and set realistic goals. These numbers are a convenient starting point, but they are general population estimates — not a substitute for a professional medical assessment, and best read alongside how you look, feel, and perform.
❓ Frequently Asked Questions
How does the BMI and body fat calculator work?
Enter your weight, height, age, and sex. It computes Body Mass Index as weight in kilograms divided by height in metres squared, sorts that into a standard category, then applies the Deurenberg equation — which uses BMI, age, and sex — to estimate your body-fat percentage.
What are the BMI categories?
The standard bands are underweight below 18.5, normal from 18.5 to under 25, overweight from 25 to under 30, and obese at 30 or above. These thresholds come from population health data and describe ranges, not individual health — muscular athletes in particular often sit above 25 while being very lean.
Why estimate body fat from BMI?
Directly measuring body fat needs tools like calipers, bioelectrical impedance, or a DEXA scan. The Deurenberg equation offers a no-equipment estimate by adjusting BMI for age and sex, which tend to correlate with body-fat percentage. It's a convenient approximation, not a precise measurement.
Is BMI reliable for athletes?
Not always. Because BMI only considers height and weight, it can't tell muscle from fat, so strength and power athletes frequently read as overweight despite low body fat. Use these figures as a rough guide alongside other markers, and remember they are general estimates, not a substitute for a professional medical assessment.